Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS6231427 B1
Publication typeGrant
Application numberUS 08/853,323
Publication dateMay 15, 2001
Filing dateMay 8, 1997
Priority dateAug 9, 1994
Fee statusLapsed
Also published asDE69512971D1, DE69512971T2, EP0696495A1, EP0696495B1, US5692947
Publication number08853323, 853323, US 6231427 B1, US 6231427B1, US-B1-6231427, US6231427 B1, US6231427B1
InventorsHomayoun Talieh, David Edwin Weldon
Original AssigneeLam Research Corporation
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Linear polisher and method for semiconductor wafer planarization
US 6231427 B1
Abstract
A wafer polisher and method for the chemical mechanical planarization of semiconductor wafers. The polisher includes a wafer holder for supporting the semiconductor wafer and a linear polishing assembly having a polishing member positioned to engage the surface of the wafer. The polishing member is movable in a linear direction relative to the wafer surface to uniformly polish the surface of the wafer. A pivotal alignment device may be used to pivotally support one of the wafer holder and the polishing member relative to the other of the wafer holder and the polishing member with the surface of the wafer and the polishing member retained in parallel alignment during operation of the polisher. The polisher optionally includes a conditioning station for conditioning the polishing member.
Images(8)
Previous page
Next page
Claims(11)
What is claimed is:
1. A polishing pad assembly for polishing a semiconductor wafer, said assembly comprising:
a belt forming a closed loop;
at least one non-abrasive polishing pad mounted on the belt, the non-abrasive polishing pad configured to receive a polishing slurry suitable for use in chemical mechanical planarization of the semiconductor wafer, wherein the non-abrasive polishing pad polishes a surface of the semiconductor wafer with the polishing slurry; and,
wherein said belt is formed of metal.
2. The invention of claim 1 wherein said belt is formed of stainless steel.
3. A polishing pad assembly for polishing a semiconductor wafer, said assembly comprising:
a first roller;
at least one additional roller;
a belt forming a closed loop, which belt is mounted on said first roller and said at least one additional roller;
at least one non-abrasive polishing pad mounted to said belt, the non-abrasive polishing pad configured to receive a polishing slurry suitable for use in chemical mechanical planarization of the semiconductor wafer, wherein the non-abrasive polishing pad polishes a surface of the semiconductor wafer with the polishing slurry; and
a drive system coupled to at least said first roller to rotate said first roller and to cause said belt and said non-abrasive polishing pad to move in a path;
wherein said belt is formed of metal.
4. The invention of claim 3 wherein said belt is formed of stainless steel.
5. A polishing pad assembly for polishing a semiconductor wafer, said assembly comprising:
a belt forming a closed loop; and
at least one non-abrasive polishing pad mounted on the belt, the non-abrasive polishing pad configured to receive a polishing slurry suitable for use in chemical mechanical planarization of the semiconductor wafer, wherein the non-abrasive polishing pad polishes a surface of the semiconductor wafer with the polishing slurry;
wherein said belt comprises a polyurethane material.
6. A polishing pad assembly for polishing a semiconductor wafer, said assembly comprising:
a first roller;
at least one additional roller;
a belt forming a closed loop, which belt is mounted on said first roller and said at least one additional roller;
at least one non-abrasive polishing pad mounted to said belt, the non-abrasive polishing pad configured to receive a polishing slurry suitable for use in chemical mechanical planarization of the semiconductor wafer, wherein the non-abrasive polishing pad polishes a surface of the semiconductor wafer with the polishing slurry; and
a drive system coupled to at least said first roller to rotate said first roller and to cause said belt and said non-abrasive polishing pad to move in a path;
wherein said belt comprises a polyurethane material.
7. A polishing pad assembly for polishing a semiconductor wafer, said assembly comprising:
a belt forming a closed loop; and
at least one non-abrasive polishing pad mounted on the belt, the non-abrasive polishing pad configured to receive a polishing slurry suitable for use in chemical mechanical planarization of the semiconductor wafer, wherein the non-abrasive polishing pad polishes a surface of the semiconductor wafer with the polishing slurry;
wherein said belt comprises a high-strength polymer.
8. The invention of claim 7 wherein the belt comprises a polyethylene terephthalate resin.
9. A polishing pad assembly for polishing a semiconductor wafer, said assembly comprising:
a first roller;
at least one additional roller;
a belt forming a closed loop, which belt is mounted on said first roller and said at least one additional roller;
at least one non-abrasive polishing pad mounted to said belt, the non-abrasive polishing pad configured to receive a polishing slurry suitable for use in chemical mechanical planarization of the semiconductor wafer, wherein the non-abrasive polishing pad polishes a surface of the semiconductor wafer with the polishing slurry; and
a drive system coupled to at least said first roller to rotate said first roller and to cause said belt and said non-abrasive polishing pad to move in a path;
wherein said belt comprises a high-strength material.
10. The invention of claim 9 wherein the belt comprises a polyethylene terephthalate resin.
11. A method of polishing a semiconductor wafer comprising:
providing a polishing pad assembly, wherein said polishing pad assembly comprises a belt forming a closed loop, at least one non-abrasive polishing pad mounted on the belt, wherein the non-abrasive polishing pad is configured to receive a polishing slurry, and wherein said belt is formed of metal;
rotating the polishing pad assembly such that the at least one non-abrasive polishing pad mounted on the belt moves in a linear direction; and
polishing the semiconductor wafer by pressing the semiconductor wafer against the polishing pad assembly.
Description

This application is a division of application Ser. No. 08/759,172, filed Dec. 3, 1996, now U.S. Pat No. 5,692,947, which is in turn a continuation of application Ser. No. 08/287,658 filed Aug. 9, 1994, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates in general to a system for chemical mechanical polishing of semiconductor wafers. More particularly, the present invention relates to a linear polisher for the chemical mechanical planarization of semiconductor wafers.

The available systems for the chemical mechanical planarization of semiconductor wafers typically employ a rotating wafer holder for supporting the wafer and a polishing pad which is rotated relative to the wafer surface. The wafer holder presses the wafer surface against the polishing pad during the planarization process and rotates the wafer about a first axis relative to the polishing pad. The polishing pad is carried by a polishing wheel or platen which is rotated about a second axis different from the rotational axis of the wafer holder. A polishing agent or slurry is applied to the polishing pad to polish the wafer. As the wafer holder and the polishing wheel are each rotated about their respective central axes, an arm moves the wafer holder in a direction parallel to the surface of the polishing wheel.

Since the polishing rate applied to the wafer surface is proportional to the relative velocity of the polishing pad, the polishing rate at a selected point on the wafer surface depends upon the distance of the selected point from the axis of rotation. Thus, the polishing rate applied to the edge of the wafer closest to the rotational axis of the polishing pad is less than the polishing rate applied to the opposite edge of the wafer. Rotating the wafer throughout the planarization process averages the polishing rate applied across the wafer surface so that a uniform average polishing rate is applied to the wafer surface. Although the average polishing rate may be uniform, the wafer surface is continuously exposed to a variable polishing rate during the planarization process.

Although the polishing rate is generally proportional to the relative velocity of the polishing pad, other factors as for example fluid dynamic and thermodynamic effects on the chemical reactions occurring during the planarization process influence the actual polishing rate at any given instant in time. These effects are not uniform across the wafer surface during the planarization process. Moreover, instead of “averaging” the effects, the relative rotation of the wafer and the polishing pad contribute to the fluid dynamics and thermodynamics of the reaction.

After a period of time, the polishing pad becomes saturated with deactivated slurry, loose particles, etc. The pad must be frequently roughened to remove such particles from the polishing surface of the pad. For example, a scraping tool is typically mounted in contact with the polishing pad to scrape the loose slurry from the pad surface.

Because of advances in wafer processing technology and semiconductor component structure, uniformly polishing or planarizing a film on the surface of the wafer has become increasingly important. For example, integrated circuits such as microprocessors, controllers and other high performance electronic logic devices have become increasing complex while the size of such devices has decreased substantially. With the multiple wiring layers employed in complex devices, a significant component of the delay in signal propagation is due to the interconnections between the multiple layers. Several multilevel interconnection processes are being developed to reduce the delays associated with interconnect resistance, such as smaller wiring geometry and the use of copper or other materials as interconnect metals. However, the surface of the semiconductor wafer is generally rough. Each wiring layer provides additional circuitry components which project from the wafer surface, producing a rippled effect on the surface of the device. When several layers are formed on the wafer, the uneven topography of the device becomes more exaggerated. Even if the first layer is completely planar, circuitry components of the succeeding layers often produce a rippled effect which must be planarized.

This invention provides a system for uniformly polishing the surface of a semiconductor wafer. The system includes a linear polisher which applies a uniform polishing rate across the wafer surface throughout the planarization process for uniformly polishing the film on the surface of the semiconductor wafer. The polisher is of simplified construction, thereby reducing the size of the machine and making the polisher suitable for even larger-diameter wafers. For example, the linear polisher is approximately ⅕ the size of available machines. The reduced size and simplicity of the machine substantially reduces the manufacturing costs of the polisher. Since less space is required for the polisher, the operation costs are also substantially reduced. Although the overall size may vary, the linear polisher may be only slightly larger than the wafer. The polisher of the invention may have one or more conditioning stations for roughing or conditioning the polishing member during the polishing cycle, ensuring that a uniform polishing rate is applied to the wafer surface throughout the planarization process.

SUMMARY OF THE INVENTION

In summary, the present invention provides a system for the chemical mechanical planarization of semiconductor wafers. The system includes a wafer polishing machine having a linear polisher and a wafer support assembly for holding a semiconductor wafer. The linear polisher includes a polishing pad positioned to engage the wafer surface. The polishing pad is moved in a linear direction relative to the wafer for uniformly planarizing the surface of the wafer. The wafer polishing machine may also include a pivotal alignment device positioned to pivotally support either the wafer holder or the polishing pad so that the wafer surface and the polishing pad are retained in parallel alignment during operation of the polishing machine.

In one embodiment of the invention, the polishing pad is movable in a continuous path during which the polishing pad passes across the surface of the wafer. The wafer polishing machine further includes a conditioning station positioned in the path of the polishing pad for conditioning the pad during operation of the polishing machine.

The system of the invention also includes a method for uniformly polishing the surface of a semiconductor wafer. The method includes the steps of supporting the wafer with the surface of the wafer engaging the polishing pad and moving the polishing pad in a linear direction relative to the wafer to apply a uniform polishing force across the wafer surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and features of the invention will be more readily apparent from the following detailed description and appended claims when taken in conjunction with the drawings, wherein:

FIG. 1 is front plan view of a wafer polishing machine in accordance with the invention;

FIG. 2 is a side plan view, partially broken away, of the wafer polishing machine of FIG. 1;

FIG. 3 is a top plan view of the wafer polishing machine of FIG. 1;

FIGS. 4A and 4B are schematic side views showing the support assembly is a raised position and a lowered position;

FIGS. 5A and 5B are schematic views of a wafer polishing machine in accordance with another embodiment of the invention;

FIG. 6 is a perspective view of a linear polisher of a wafer polishing machine in accordance with another embodiment of the invention;

FIG. 7 is a schematic view of the wafer polishing machine of FIG. 6;

FIG. 8 is a perspective view of a linear polisher in accordance with still another embodiment of the invention; and

FIG. 9 is a view similar to FIG. 8 of a linear polisher in accordance with another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiment, which is illustrated in the accompanying figures. Turning now to the drawings, wherein like components are designated by like reference numerals throughout the various figures, attention is directed to FIGS. 1-3.

A wafer polishing machine 10 for uniformly planarizing the surfaces of a semiconductor wafer 8 is shown in FIGS. 1-3. The polishing machine 10 generally includes a linear polisher 12 having a polishing member or polishing pad 14 for polishing the surface 9 of the semiconductor wafer 8 and a support assembly 16 for supporting the semiconductor wafer during the polishing operation. A polishing agent or slurry (not shown) such as a colloidal silica or fumed silica slurry is deposited on the polishing member to polish the wafer surface. Alternatively, the polishing member 14 may be provided by a pad impregnated with an abrasive polishing agent. The linear polisher 12 moves the polishing pad 14 in a linear direction relative to the semiconductor wafer 8 to continuously provide a uniform polishing force across the entire surface of the wafer. Preferably, the polishing member 14 is moved at a constant velocity although in some applications it may be desirable to employ a specific variable velocity profile to polish the wafer surface. The linear, constant velocity motion of the polishing member 14 provides superior polishing uniformity across the wafer surface.

In the embodiment of the linear polisher 12 shown in FIGS. 1-3, the polishing member or pad 14 is mounted to the outer surface of an endless belt 18. The belt 18 extends across a support plate 20 and is mounted to a pair of rollers 22 and 24. A motor assembly 26 coupled to the rollers 22 and 24 drives the rollers so that the belt 18 is moved at a constant velocity in the direction indicated by arrow A. As the belt is moved by the rollers, the belt 18 travels across the support surface 20. The support surface 20 rigidly supports the belt 18 opposite the support assembly 16 to ensure that the polishing member 14 applies a uniform polishing force across the entire surface of the wafer. Preferably, the velocity at which the belt is moved is within the range of approximately 50 to 150 feet per minute for optimum planarization of the wafer surface. However, it is to be understood that depending upon the chemistry employed, the velocity may also be considerably faster, for example up to 300 feet per minute or more. A fluid layer, generally designated 28, between the inner surface of the belt 18 and the support plate 20 reduces frictional losses and minimizes heat dissipation during operation of the linear polisher 10. The fluid layer 28 may also permit minimal deflection of the belt 18 relative to the support plate as it passes across the plate 20 to facilitate the parallel alignment of the wafer surface and the polishing member 14.

The polishing member 14 preferably extends the entire circumference of the endless belt 18 and has a width greater than the diameter of the wafer 8. However, the size of the polishing member may be varied as desired. The polishing pad 14 is affixed to the belt 18 using any suitable securement means. If the polishing member is originally rectangular in shape, the overlapping edges of the polishing member 14 are tapered so that the wafer 8 tends to press the uppermost edge of the polishing member against the underlying edge. In the present embodiment, the polishing member 14 is a pad of stiff polyurethane material, although other suitable materials may also be used. The endless belt may be formed of a metal such as stainless steel, high strength polymers such as polyethylene terephthalate resin, or other suitable flexible materials having sufficient strength to withstand the loads applied to the belt by the wafer 8. In the embodiment shown in FIGS. 1-3, the endless belt 18 is carried by two rollers 22 and 24. However, it is to be understood that the number of rollers may be increased as desired. The rollers 22 and 24 retain the belt 18 under tension so that the polishing member 14 is sufficiently rigid to uniformly polish the surface of the wafer. The tension of the belt may be increased or decreased as necessary by adjusting the position of roller 24 relative to roller 22.

The support assembly 16 retains the wafer 8 in position during the polishing operation. In the embodiment shown in FIGS. 1-3, the support assembly 16 also maximizes the parallel alignment between the wafer surface 9 and the polishing member 14 and applies a downward force pushing the wafer surface 9 against the polishing member 14 so that the polishing member 14 applies the required polishing force across the surface of the wafer. As shown particularly in FIG. 2, the support assembly 16 includes a wafer holder 34 for supporting the wafer 8 and accurately aligning the wafer surface 9 with the polishing member 14. The wafer holder 34 has a lower plate 36 formed with a disc-shaped recess shaped to receive the wafer 8 with the wafer surface 9 projecting slightly from the lower plate 36. The wafer 8 is held in place by a backing film, waxing or another suitable technique. The lower plate 36 is affixed to a spherical-shaped journal 40 supported in a bearing 42. In the present embodiment, the clearance spacing between the journal 40 and the bearing 42 is filled with a lubricant such as water, another slurry compatible liquid or a suitable gas. The lubricant-filled cavity is coupled to a reservoir (not shown) in which a supply of lubricant is retained under pressure to provide a hydrostatic bearing in which the journal 40 is completely isolated from the bearing 42 at all times.

The spherical curvature of the journal 40 and bearing 42 provides a pivotal support for the wafer 8 which retains the wafer surface 9 at an orientation parallel to the surface of the polishing member 14 regardless of the shear forces applied to the wafer surface during the polishing process. In the present embodiment, the journal 40 is shaped in the form of a slab or section of a sphere having a center located at pivot point 46 located on the surface 9 of the wafer as shown in FIGS. 1 and 2. In other words, the shape of the journal 40 may be obtained by sectioning the sphere into two hemispheres and then removing a slice having the same thickness as the wafer from the planar surface of one of the hemispheres. This ensures that the pivot point 46 is located on the surface of the wafer. As shown in FIGS. 1 and 2, a section may optionally be removed from the opposite end of the hemisphere to reduce the height of the journal 40.

The journal 40 pivots within the bearing 42 to provide the wafer surface 9 and the polishing pad 14 with a substantially parallel orientation throughout the polishing operation. The journal 40 pivots about the pivot point 46 so that the surface of wafer having a tapered thickness is parallel to the polishing member 14. The journal also accommodates variations in the thickness of the belt 18 and polishing member 14 so that the parallelism between the wafer surface 9 and the polishing member 14 is maintained. When the wafer surface is positioned against the moving polishing belt 14, shear frictional forces are applied across the wafer surface. Since the frictional forces applied to the wafer essentially pass through the pivot point 46, the frictional forces will not cause the journal 40 to pivot relative to the bearing 42. Instead, the journal 40 continues to position the wafer with the wafer surface 9 parallel to the polishing member 14. Thus, by positioning the pivot point of the journal 40 on the wafer surface 9, the wafer holder 34 of the invention maintains the parallelism between the wafer surface 9 and the polishing member 14 so that the entire wafer surface may be uniformly polished.

As the wafer is polished and the thickness of the wafer is reduced, the pivot point 46 become displaced from the surface of the wafer. Often, the change in wafer thickness is so small that the parallel alignment of the wafer surface and the polishing member 14 will not be significantly affected. However, if greater precision is required, journal 40 may be formed with a wedge shaped section (not shown). As the wafer thickness is reduced, the wedge shaped section slides relative to the remainder of the journal to maintain the wafer surface at the center of the sphere or pivot point 46. Depending upon the vibrational effect of the polishing machine 10, it may also be desirable to include a closed-loop control system (not shown) to provide damping since the journal 40 and bearing 42 are substantially frictionless.

The wafer holder 34 is mounted to a horizontally extending upper platform 48 positioned above the support plate 20 of the linear polisher 12. The upper platform 48 is carried by a vertically extending back plate 50. The back plate 50 is pivotally mounted to the linear polishing assembly 12 by a transversely extending pivot bar 52. The support assembly 16 may be easily moved away from the polishing member 14, endless belt 18 and support plate 20 for insertion and removal of the wafer or maintenance of the support assembly or linear polisher by pivoting the assembly 16 about the bar 52.

The upper platform 48 of the support assembly 16 is coupled to the linear polisher by a pneumatic cylinder 54. When the pneumatic cylinder is actuated, the cylinder 54 urges the platform 48 toward the support plate 20 to press the wafer 8 against the polishing member 14 of the linear polisher. FIGS. 4A and 4B schematically show the support assembly 16 in a raised position and a lowered position, respectively. By moving the upper platform 48 downward, the required polishing force is applied to the surface of the wafer for planarizing the wafer surface. The magnitude of the polishing force applied to the wafer surface 9 may be precisely controlled by controlling the operation of the pneumatic cylinder 54. In other embodiments of the invention, a hydraulic cylinder or other device may be used instead of the pneumatic cylinder 54 to move the upper platform 48 toward the support plate 20.

Preferably, the support assembly 16 slowly rotates the wafer 8 relative to the polishing member as the polishing member 14 is moved in linear direction. When the polishing member 14 engages the wafer 8, polishing pathways are formed on a microstructural level. Slow rotation of the wafer allows for polishing to occur at random incidence (i.e. in random directions), an important factor in defining geometric structures with polishing and preventing the formation of defined scratches in the polished surface. With most surface configurations, it is generally desirable to provide the pathways with random trajectories. Slowly rotating the wafer also varies the location of the leading edge to obtain uniform polishing along the edge of the wafer. In the present embodiment, the wafer holder 34 is slowly rotated relative to the polishing member 14 by a motor (not shown) at a slow rate. The rate of rotation of the wafer holder 34 is less than {fraction (1/10)} of the speed of the belt 18 and is selected so that the wafer undergoes a number of full revolutions during the polishing operation to achieve uniform polishing. At a minimum, the wafer be rotated for a full rotation during the polishing process. Rotating the wafer for less than a full revolution may provide the wafer surface with a non-uniform profile.

The uniform polishing rate applied across the wafer surface by the linear motion of the polishing member 14 and the parallelism achieved between the wafer surface 9 and the polishing member 14 allows for uniform polishing with increased precision. This is of particular advantage in the processing of semiconductor wafers, where one may wish to remove one micron from a film having a thickness of two microns.

A wafer polishing machine 10 a in accordance with another embodiment of the invention is shown schematically in FIGS. 5A and 5B. Referring particularly to FIG. 5A, the polishing machine 10 a generally includes a linear polisher 12 a having a polishing member 14 a mounted to an endless belt 18 a which is carried by a plurality of rollers 65. The semiconductor wafer is retained by a support assembly 16 a with the surface of the wafer positioned to engage the polishing member 14 a. The belt 18 a moves the polishing member 14 a in a linear direction relative to the wafer to uniformly polish the surface of the wafer.

As the polishing member 14 a polishes the wafer surface 9, used slurry collects within the pores in the polishing material and reduces the roughness of the polishing member 14 a. The polishing member must be periodically conditioned to remove the deactivated slurry and roughen the polishing member 14, thereby maximizing the effectiveness of the polishing member 14 a in uniformly planarizing the wafer surface. In the embodiment shown in FIGS. 5A and 5B, the linear polisher 12 a includes a conditioning station 66 for conditioning the polishing member 14 a during the polishing cycle. After a given section of the polishing member 14 a passes across the wafer surface, it travels through the station 66 where it is conditioned before returning to the wafer surface 9. With the conditioning station 66, the wafer surface is continuously exposed to a freshly conditioned section of the polishing member 14 a. Using a continuously conditioned pad to polish the semiconductor wafer provides greater control over the planarization process and ensures that the wafer surface is continuously exposed to a uniform polishing force.

In the embodiment shown in FIG. 5A, the conditioning station 66 includes a scraping member 70 such as a diamond conditioning block positioned to engage the surface of the polishing member 14 a after it leaves the wafer. The scraping member 70 removes loose slurry and other loose particles from the member 14 a and roughens the surface of the polishing member. The polishing member 14 a then passes through an acid bath 72, a rinse bath 74 and a slurry bath 76 for further conditioning. The acid bath 72 contains an acidic solution such as diluted hydrofluoric acid solution to remove the remainder of the deactivated slurry from the polishing member 14 a. The rinse bath 74 is filled with a rinsing solution such as distilled water for removing any traces of the acidic solution from the polishing member. Fresh slurry, such as a colloidal silica dispersion, is applied to the polishing member 14 a in the slurry bath 76. The belt 18 a travels past the scraping member 70 and enters the acid bath 72. From the acid bath 72, the belt 18 a passes through a first seal 78 into the rinse bath 74 and through a second seal 80 into the slurry bath 76. The seals 78 and 80 substantially prevent intermixing of the contents between the adjacent baths 72, 74 and 76. After the belt 18 a leaves the slurry bath 72, the freshly conditioned polishing member 14 a is passed across the wafer to polish the wafer surface.

The scraping member 70 and the series of the baths 72, 74 and 76 illustration one configuration of a conditioning station which is particularly suitable for conditioning the polishing member 14 a during operation of the wafer polishing machine 10 a. However, it is to be understood that other embodiments of the invention are subject to considerable modification. For example, instead of seals 78 and 80 separating the acid bath 72, rinse bath 74 and slurry bath 76, additional rollers may be provided to direct the belt into the individual baths. The number of baths provided in the conditioning station may be increased or decreased as desired. Instead of baths, the conditioning system may employ nozzles 82 as shown in FIG. 5B for spraying cleaning agents, rinsing agents and/or slurry on the polishing member 14 a. Further, the conditioning system may include a combination of baths and spray injection nozzles.

FIGS. 6 and 7 illustrate another embodiment of a linear polisher 12 b in accordance with the invention. The polishing machine 10 b includes a linear polisher 12 b having a polishing member 14 b carried by an endless belt 18 b and a support assembly 16 b (FIG. 7) for supporting a semiconductor wafer. As shown in FIG. 7, a wafer holder 86 mounted to the support assembly 16 b rigidly supports the semiconductor wafer during the polishing operation. A gimballed support 88 positioned beneath the belt 18 b supports the belt 18 b and applies an upward force to the belt to press the polishing member 14 b against the wafer for polishing the wafer surface. The gimballed support 88 also aligns the belt 18 b with the polishing member 14 b parallel to the wafer surface so that a uniform polishing force is applied across the entire surface of the wafer.

In the embodiment shown in FIGS. 6 and 7, the construction of the gimballed support 88 is substantially similar to the wafer support 34 shown in FIGS. 1-3. The gimballed support 88 includes a spherical shaped journal 90 supported in a hydrostatic bearing 92. The clearance space between the journal 90 and the bearing 92 is filled with a lubricant such as water, another slurry compatible liquid or a suitable gas. A reservoir (not shown) retaining lubricant under pressure supplies the clearance space with lubricant to ensure that the journal is constantly separated from the interior of the bearing. The journal 90 has a planar support surface which engages the underside of the belt and presses the polishing member 14 b against the wafer surface.

As shown in FIG. 7, the journal 90 is formed in the shape of a section of a sphere which has a center at pivot point 96 positioned on the exterior of the polishing member 14 b. The journal pivots within the bearing 92 about the pivot point 96 to maintain the parallelism between the wafer surface 9 and the polishing member 14 b. As the polishing member 14 b polishes the wafer surface, shear frictional forces are applied to the polishing member by the wafer surface. Since the frictional forces essentially pass through the pivot point 96, the frictional forces will not cause the journal 90 to pivot relative to the wafer surface. Thus, the parallelism between the surface of the wafer and the polishing member 14 b is continuously maintained while the wafer surface is polished.

Instead of the endless belt of the previously described embodiments, other apparatus may be used to move the polishing member in a linear direction. FIG. 8 shows a linear polisher 12 c having a plurality of parallel reciprocating bars 106 positioned on a support plate 20 c. A polishing member 14 c is mounted to each of the reciprocating bars 106 for polishing the surface of the semiconductor wafer 8. Although not shown, the bars 106 may be positioned in a slurry bath to ensure that sufficient slurry is applied to the polishing members 14 c. Alternatively, the bars 106 may be inverted and suspended above the wafer and the slurry applied to the wafer surface. An actuating device such as pneumatic cylinders 108 coupled to the reciprocating bars by pins 110 move the bars in a linear direction across the support plate 20 c. Although not shown, the bars 106 may be carried by linear slides or a linear motor. Preferably, the bars 106 are divided into two groups which are simultaneously moved in opposite directions by the pneumatic cylinders 108. As shown in FIG. 8, the linear polisher 12 c includes four reciprocating bars with each bar 106 moving in an opposite direction from adjacent bars. However, it is to be understood that the number of reciprocating bars may be increased or decreased as desired and that numerous other configurations may be employed. Further, additional pneumatic cylinders may be used to independently move the reciprocating bars.

The pneumatic cylinders 108 move the reciprocating bars 106 back and forth relative to the semiconductor wafer, with the stroke of the bars 106 preferably being approximately equivalent to the diameter of the wafer plus two times the length of the reciprocating bars so that with each stroke the bar moves beyond the wafer surface. Alternatively, the reciprocating bars may oscillate so that the bar is continuously in contact with the wafer surface. The reciprocating bars 106 have greater rigidity than the endless belt of the previously described embodiments, providing a more stable system. The velocity of the reciprocating bars 106 is controlled by a control system 112 coupled to the pneumatic cylinders 108. The control system 112 is preferably configured to actuate the cylinders and drive the reciprocating bars 106 at a constant velocity. The constant velocity, linear motion of the polishing members 14 c uniformly polishes the surface of the wafer. However, with some surface configurations it may be desirable to move the polishing members 14 c in a non-uniform velocity profile. With the present embodiment, the control system may be configured to actuate the pneumatic cylinders 108 in accordance with a specific velocity profile to move the polishing members 14 c at the required non-uniform velocity for uniform polishing. Although pneumatic cylinders 108 are employed in the present embodiment, other devices such as hydraulic cylinders, cams, stepping motors used with a ball screw etc., servomotors, linear motors, etc. may also be used to move the reciprocating bars 106.

The wafer 8 is preferably supported by the support assembly 16 shown in FIGS. 1-3 with the pivotal movement of the wafer within the wafer holder 34 positioning the wafer surface 9 parallel to the surface of the polishing members 14 c. As described above in relation to FIGS. 1-3, the wafer holder 34 may rotate the wafer 8 relative to the polishing members 14 c to uniformly planarize localized regions of the wafer surface. Alternatively, with some surface configurations uniform planarity may be obtained without rotating the wafer. Although not shown, the support assembly 16 may be mounted for movement in a transverse direction relative to the reciprocating bars to move the wafer 8 transversely across the surface of the polishing members 14 c.

The linear polisher 12 d shown in FIG. 9 includes a plurality of reciprocating bars 106 d which are moved across a support plate 20 d by a crank assembly 118. Polishing members 14 d are mounted to the reciprocating bars 106 d for polishing the surface of the wafer. The crank assembly 118 includes a plurality of crank arms 120 each coupled to a crank shaft 122 and one of the reciprocating bars. A motor (not shown) rotates the crank shaft 122, causing the crank arms 120 to move the reciprocating bars in a linear direction. As shown in FIG. 9, the crank arms 120 move adjacent reciprocating arms in opposite directions. However, in other modifications two or more adjacent bars may be moved in the same direction. The linear polisher 12 d is used with the support assembly 16 shown in FIGS. 1-3, which supports the wafer and positions the wafer surface parallel to the polishing members 14 d.

In the embodiment of FIG. 9, the velocity of the reciprocating bars 106 d is not constant. Instead, the crank assembly 118 moves the reciprocating bars 106 d at a sinusoidal velocity. Preferably, the semiconductor wafer is rotated at a variable velocity defined by the sinusoidal variations in the velocity of the polishing members 14 d. With the crank assembly 118, the reciprocating bars 106 d may be moved in a specific variable velocity profile to provide the desired polishing across the wafer surface.

Except as set forth above, the modifications of FIGS. 4A-4B, 5A-5B, 6-7, 8 and 9 resemble those of the preceding modifications and the same reference numerals followed by the subscripts a-d, respectively, are used to designate corresponding parts.

It is to be understood that in the foregoing discussion and appended claims, the terms “wafer surface” and “surface of the wafer” include, but are not limited to, the surface of the wafer prior to processing and the surface of any layer formed on the wafer, including oxidized metals, oxides, spun-on glass, ceramics, etc.

While the invention has been described with reference to a few specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US619399Aug 23, 1898Feb 14, 1899 Glass grinding and polishing machine
US2187743 *Apr 28, 1938Jan 23, 1940Carborundum CoGranular coated article
US3427765 *Feb 11, 1966Feb 18, 1969Carborundum CoAbrasive belts and method of making same
US3447306Sep 16, 1966Jun 3, 1969Barnes Drill CoAbrading machine
US3654739Feb 5, 1970Apr 11, 1972Metabowerke KgBelt grinding or polishing machine
US3753269May 21, 1971Aug 21, 1973Budman RAbrasive cloth cleaner
US3906678Dec 26, 1973Sep 23, 1975Buehler LtdAutomatic specimen polishing machine and method
US4016857Nov 24, 1975Apr 12, 1977Hall George HEpoxy bond diamond saw
US4347689Oct 20, 1980Sep 7, 1982Verbatim CorporationMethod for burnishing
US4416090May 13, 1982Nov 22, 1983Landskrona Produktion AbBelt sanding machine
US4593495Nov 26, 1984Jun 10, 1986Toshiba Machine Co., Ltd.Polishing machine
US4628640Jan 17, 1985Dec 16, 1986Johannsen Hans PeterBelt sander apparatus
US4642943Nov 21, 1985Feb 17, 1987Taylor Jr Joseph RBelt abrading apparatus and method
US4651474 *Jun 13, 1986Mar 24, 1987Timesavers, Inc.Wide belt sanding machine with platen oscillating means
US4704823Sep 2, 1986Nov 10, 1987Acrometal Products, Inc.Abrasive surfacing machine
US4811522Mar 23, 1987Mar 14, 1989Gill Jr Gerald LCounterbalanced polishing apparatus
US4934102Oct 4, 1988Jun 19, 1990International Business Machines CorporationSystem for mechanical planarization
US4941293Feb 7, 1989Jul 17, 1990Ekhoff Donald LFlexible rocking mount with forward pivot for polishing pad
US5081795Jan 22, 1991Jan 21, 1992Shin-Etsu Handotai Company, Ltd.Polishing apparatus
US5205082Dec 20, 1991Apr 27, 1993Cybeq Systems, Inc.Wafer polisher head having floating retainer ring
US5212910Jul 9, 1991May 25, 1993Intel CorporationComposite polishing pad for semiconductor process
US5230184Jul 5, 1991Jul 27, 1993Motorola, Inc.Distributed polishing head
US5232875Oct 15, 1992Aug 3, 1993Micron Technology, Inc.Method and apparatus for improving planarity of chemical-mechanical planarization operations
US5246525Jun 25, 1992Sep 21, 1993Sony CorporationApparatus for polishing
US5274964Aug 19, 1992Jan 4, 1994Abrasive Cleaning Systems, Inc.Dry abrasive belt cleaner
US5276999Jun 6, 1991Jan 11, 1994Bando Kiko Co., Ltd.Machine for polishing surface of glass plate
US5287663Apr 28, 1992Feb 22, 1994National Semiconductor CorporationPolishing pad and method for polishing semiconductor wafers
US5297361Jul 16, 1993Mar 29, 1994Commissariat A L'energie AtomiquePolishing machine with an improved sample holding table
US5329732Jun 15, 1992Jul 19, 1994Speedfam CorporationWafer polishing method and apparatus
US5329734Apr 30, 1993Jul 19, 1994Motorola, Inc.Polishing pads used to chemical-mechanical polish a semiconductor substrate
US5335453Sep 27, 1993Aug 9, 1994Commissariat A L'energie AtomiquePolishing machine having a taut microabrasive strip and an improved wafer support head
US5341609 *Jun 16, 1993Aug 30, 1994Minnesota Mining And Manufacturing CompanyAbrasive belts and their manufacture
US5383309 *Nov 9, 1993Jan 24, 1995Norton CompanyAbrasive tool
US5399125Jun 11, 1993Mar 21, 1995Dozier; Robert L.Belt grinder
US5454844 *Oct 29, 1993Oct 3, 1995Minnesota Mining And Manufacturing CompanyAbrasive article, a process of making same, and a method of using same to finish a workpiece surface
US5456627Dec 20, 1993Oct 10, 1995Westech Systems, Inc.Conditioner for a polishing pad and method therefor
US5782679 *Sep 23, 1996Jul 21, 1998Hunter; David T.Metal abrasive belt and method of making same
DE3411120A1Mar 26, 1984Nov 8, 1984Toto LtdLapping device
EP0517594A1Jun 4, 1992Dec 9, 1992Commissariat A L'energie AtomiquePolishing machine with a tensioned finishing belt and an improved work supporting head
EP0517595A1Jun 4, 1992Dec 9, 1992Commissariat A L'energie AtomiquePolishing machine with pressure control
JPH02269552A Title not available
JPH02269553A Title not available
JPH04250967A Title not available
JPH07111256A Title not available
JPS59232768A Title not available
JPS62162466A Title not available
JPS63200965A Title not available
JPS63251166A Title not available
JPS63267155A Title not available
RU2007784C1 Title not available
WO1994017957A1Feb 8, 1994Aug 18, 1994Rodel IncApparatus and method for polishing
Non-Patent Citations
Reference
1"A New Pad and Equipment Development for ILD Planarization" by Toshiyasu Beppu, Motoyuki Obara and Yausuo Minamikawa, Semiconductor World, Jan., 1994, MY Mar. 17, 1994.
2"Application of Chemical Mechanical Polishing to the Fabrication of VLSI Circuit Interconnections", William J. Patrick, William L. Guthrie, Charles L. Stadley and Paul M. Schiable, J. Electrochem. Soc., vol. 138, No. 6, Jun. 1991, pp. 1778-1784.
3"Theory & Practice of Lubrication for Engineers", Dudley Fuller, Wiley-Interscience, 1st ed., pp. 22-25 and 86.
4Practical Ideas, Jun. 1994, p. 67.
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6475293 *Nov 16, 2000Nov 5, 2002Intel CorporationRotating belt wafer edge cleaning apparatus
US6500056Jun 30, 2000Dec 31, 2002Lam Research CorporationLinear reciprocating disposable belt polishing method and apparatus
US6520843 *Oct 26, 2000Feb 18, 2003StrasbaughHigh planarity chemical mechanical planarization
US6572731Jan 18, 2002Jun 3, 2003Chartered Semiconductor Manufacturing Ltd.Self-siphoning CMP tool design for applications such as copper CMP and low-k dielectric CMP
US6726545Apr 26, 2002Apr 27, 2004Chartered Semiconductor Manufacturing Ltd.Linear polishing for improving substrate uniformity
US6746320Apr 30, 2002Jun 8, 2004Lam Research CorporationLinear reciprocating disposable belt polishing method and apparatus
US6827822Nov 9, 2001Dec 7, 2004Temple University Of The Commonwealth System Of Higher EducationMethod and apparatus for increasing and modulating the yield shear stress of electrorheological fluids
US7025660Aug 15, 2003Apr 11, 2006Lam Research CorporationAssembly and method for generating a hydrodynamic air bearing
US7241207 *Jul 22, 2003Jul 10, 2007Jurgen HeesemannGrinding machine and method for grinding a workpiece
WO2003042765A2 *Oct 23, 2002May 22, 2003Univ TempleMethod and apparatus for increasing and modulating the yield shear stress of electrorheological fluids
WO2007027486A2 *Aug 23, 2006Mar 8, 2007Applied Materials IncMethod for conditioning a polishing pad
Classifications
U.S. Classification451/41, 451/531, 451/288, 451/378, 451/489, 451/537, 451/534, 451/533, 451/401, 451/400, 451/387, 451/536
International ClassificationB24B37/04, B24B41/06, H01L21/304, B24B21/00, B24B53/007, B24B7/22, B24B35/00, B24B21/04
Cooperative ClassificationB24B21/04, B24B53/017, B24B35/00, B24B7/228, B24B41/06, B24B37/04
European ClassificationB24B53/017, B24B37/04, B24B41/06, B24B7/22E, B24B35/00, B24B21/04
Legal Events
DateCodeEventDescription
Jul 7, 2009FPExpired due to failure to pay maintenance fee
Effective date: 20090515
May 15, 2009LAPSLapse for failure to pay maintenance fees
Nov 24, 2008REMIMaintenance fee reminder mailed
May 18, 2008ASAssignment
Owner name: APPLIED MATERIALS, INC., CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LAM RESEARCH CORPORATION;REEL/FRAME:020951/0935
Effective date: 20080108
Sep 16, 2004FPAYFee payment
Year of fee payment: 4
Jan 10, 2000ASAssignment
Owner name: LAM RESEARCH CORPORATION, CALIFORNIA
Free format text: MERGER;ASSIGNOR:ONTRAK SYSTEMS, INC.;REEL/FRAME:010531/0127
Effective date: 19990625
Owner name: LAM RESEARCH CORPORATION 4650 CUSHING PKWY FREMONT
Owner name: LAM RESEARCH CORPORATION 4650 CUSHING PKWY FREMONT
Free format text: MERGER;ASSIGNOR:ONTRAK SYSTEMS, INC.;REEL/FRAME:010531/0127
Effective date: 19990625